She was really in her bag on this. Bran is legit doing sick shit vocally on this song the more I listen. The light and airy tones in the backgrounds, the fuller tone she uses on the verses...
Then, at the end of her 1st verse, near the end of the phrase, her vibrato is fast, and she kinda slows the speed of it towards the end of it...

I've never heard anyone exercise that kind of control of their vibrato. It's just the way SHE does it, makes it so unique.